1. Field of the Invention
The present invention relates to an air-bag arrangement, and more particularly relates to an air-bag arrangement intended to provide protection for an occupant of a vehicle in the event that an accident should occur.
2. Description of Related Art
It has been proposed to provide an air-bag which, in the event of an accident situation arising, becomes inflated to provide a protective “cushion” in front of or adjacent an occupant of a motor vehicle. Whilst initially it might be thought that a substantially air-tight air-bag would be preferred, to ensure that the air-bag remains inflated for a maximum period of time, it has been found that it is preferable to include at least one air-vent in an air-bag, since otherwise an occupant would simply rebound from the air-bag when hitting it. An air-bag provided with a vent hole provides an ideal “cushioning” effect, even though the air-bag will, of course, become deflated quite rapidly following deployment of the air-bag. However, air-bags are typically deployed, by appropriate sensors, at such a time that the air-bag is inflated when an occupant of a seat, to be protected by the air-bag, actually moves into contact with the air-bag.
It has now been found that ideally the internal pressure of the air-bag, or the “cushioning” effect provided by the air-bag, should be adjusted in dependence upon various parameters, such as, for example, the size of the seat occupant, the position of the seat occupant and whether the seat occupant is wearing a seat-belt or not. An unbelted seat occupant may require a rather “stiffer” air-bag than a belt seat occupant. Also, a larger occupant requires a “stiffer” air-bag than a smaller occupant. However, an occupant sitting close to the air-bag should be provided with a relatively “soft” air-bag if at all possible.
Attempts have been made to provide air-bags with these characteristics by sensing the relative parameter and by adjusting the amount of gas injected into the air-bag by means of the gas generator. Such arrangements are relatively complex and thus expensive.